PURPOSE: To obtain a pure compound without forming by-products by reading phenylurea with an amine.

CONSTITUTION: Phenylurea of the formula I is reacted with an amine of the formula II in an inert solvent (e.g. toluene) at a temp. from 100 to 200°C, the reaction is interrupted before by-products are formed, thereby obtaining the compounds of the formula III. The equivalent weights of the compound of the formula I and the compound of the formula II are used, and the ureacted starting material can be returned to the process of the reaction system for reutilization. In the formula I, R is phenyl, phenylene; (n) is 1 or 2. In the formula II, R1, R2 are each an alkyl, when R1 is H, an alkyl, R2 is an alkyl, phenyl respectively, and R1 and R2 together combine with N to form an aliphatic heterocyclic ring.